PowerShot /img/avatar7.jpgs virtual must-read
I got my a650 to work shooting raw tonight. actually it wasn't too hard...just finally got the right code, code that actually works. The CHDK hack has been available for a while for the PowerShot family, it took a while to get the bugs worked out of the a650 distro I guess. you can get it here, for your powershot: regardless of whatever camera make you have, just save the diskboot.bin file to the root directory of an sd card formatted in fat16, use the bootdisk.exe program to make it bootable, lock the card, pop it in and away you go. I had to use dcraw to convert the files, and also the image toolkit referred to on the dcraw home page. dcrawMS -v -w -o1 -W -q 3 %1..

Comments (10)

Now for the stunning news the a650 puts out very little noise shooting raw even at iso1600. shooting jpeg, the camera will begin to destroy the image even at ISO200, even at ISO200 it's full of white pasty stuff. ISO1600 is a disaster, for shooting jpeg. What Canon is apparently doing is mucking up the image, when shooting jpeg, to keep powershot owners drifting up the scale to their higher-end cameras. Especially now that the a650 has IS. there's noticeable chroma noise at iso1600 of course but nothing that NI can't handle easily.

The shots look fine at 2MP especially after running through NI using the default settings. I've run it on the unsharpened and sharpened raw output of dcraw through ISO1600 with little difference in output IQ. The only problem is that I can only get about 95 raw shots on a 2GB card. This could go up if I could disable the jpeg output altogether, or figure out how to format a sdhc card in fat16 with my usb card reader (apparently there's some trick in using multiple partitions) but my usb reader will only show the card if it's formatted and it will only format the card in fat32, the card needs to be in fat16 to work with this hack. Of course it is not as convenient to use as a G9 or DSLR, but this camera is $100 less than the G9, in my opinion has better controls and of course the flip lcd, shoots in continuous mode and has a much more robust case, and probably has the same optics and sensor..

Comment #1

Here's a 1600x1200 crop from a ISO1600 shot, 12MP, straight out of dcraw, no sharpening or contrast applied. If you want to get an idea of what the full image would look like when displayed at full-screen, reduce this to 50% on display the exposure is -1eV because I started at ISO80 in room light. Attachments:.


Comment #2

It obviously does not look this bad. Attachments:.


Comment #3

But, if you own a cheap powershot that is supported by this hack and you want to see what all the rage is about with raw-shooting, DLSRs, etc, now you can see easily. beware that none of the standard raw-conversion tools will read these raw files because the cameras do not officially shoot raw, so you'll get "the full Monty"...

Comment #4

Thank you for the info, I will look into it. You really like your 430EX with the G6 though?..

Comment #5

Thank you Touristguy87 for sharing your experience with the hack for the Canon A 650. The images: 1600 ISO are the first comparisons I've seen posted. Aside from the high ISO advantage, do you think the image quality in bright light/low ISO is significantly better with the A 650 shooting raw? I've read that the bit depth is significantly larger with raw and that post processing IQ is quite limited by jpeg bit depth, however this seems likely to be more significant with printed images. For online sharing and screen viewing, is there really much difference ?

Comment #6

I fixed the missing exif data problem, by copying the exif data from the camera jpegs (the companion jpegs that are taken when the camera is shot in raw mode),with exiftool... then I had to go and shoot a whole new set of calibration charts for Neat Image...right about then the batteries began to run out in the camera...another plus for the G9...also the G9 lens seems slightly sharper in the corners. it's hard to be positive about that, so much of this depends on the raw converter and NR, but the G9 shots look consistently sharper in the upper right hand corner at least. Not a huge difference but still noticeable at full-image. then there is something about "ISO override" in this chdk bios but I couldn't get anything beyond ISO1600 with the a650. still the camera is quite clean at high ISO, I wish this had worked the first time that I tried it, I probably would never have gotten a G9.

But it's not all that much better. I can see why the a650 is still about $350 and the G9 has come down $150 since intro...

Comment #7

"Aside from the high ISO advantage, do you think the image quality in bright light/low ISO is significantly better with the A 650 shooting raw? I've read that the bit depth is significantly larger with raw and that post processing IQ is quite limited by jpeg bit depth, however this seems likely to be more significant with printed images. For online sharing and screen viewing, is there really much difference ?" ...well, the smaller the display format the less that it matters, but still, the loss of quality to NR is still very noticeable even at ISO80 and in my opinion even at ISO200 I would rather shoot raw. Canon seems to be doing two things in this camera, to much up what is really pretty-good raw IQ. One is use strong NR even at low ISO and then sharpen the hell out of the images to make up for the loss of detail. This makes all t he lines very severe, gives the images a lot of "punch" but it doesn't look real. They do this even more with the a700/a700.

It really mucks-up the image, giving it a whitish-gray overtone (even with a contrast-boost), and it is clear to shoot the G9 raw at ISO200 and the a650 jpeg at ISo200 you can see it clearly. The color just does not look natural. All of this goes away when shooting raw. In exchange you get some chroma noise but hardly anything serious. Even at ISO800 it's not noticable at full-image.

There is no NR on this image. The NR'd version of the image doesn't have the white grainy dust that you can see on the wood to the left where the fence meets the don't even want to see the camera jpeg. the major difference that I see between this shot and a corresponding g9 raw shot is the sharpness of the bush in the top right corner, and the colors are a little more punched-up, that's because I could use bibble-pro for the raw converter and it was able to read the tone curve out of the camera. DCraw is not able to read the tone curve out of the a650 raw files, so it had to just guess what to use there, and it used something decent but not all that great. Still the images look WAY better than the camera jpegs.



Comment #8

...I think that you'll just get cleaner lines and better colors not to mention much-better shadow-detail shooting raw with this camera even at ISO80, and I will check that out tomorrow, it'll only take a shot or two to show the difference. It's really clear that Canon is messing-up the output from this camera to save the upper half of it's product-line...

Comment #9

Ok what the hell, here's the camera jpeg. I saved it as S-fine, to save space on the 2GB card for raw files...I also shoot the camera with the sharpness and contrast completely off (to minimize image distortion and maximize dynamic range) and then post process the same way that I PP the raw files... this has been PP'd the same as above. It's 640x480 so bump it up to 200% to get a comparable view. You may say "well, it doesn't look too bad, other than slightly washed-out" but that's for a subject that is 10 feet in front of the camera. All the "washed-out" part that you see will get exponentially worse the farther away the subject is, or the scene, is.

The plants don't look too bad, that is because they are big and close. Attachments:.


Comment #10

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